Fix challenges dir

src/symbols/factory.rs

@@ -78,7 +78,7 @@ impl<'b, C: 'b + CommandRunner, P: 'b + Policy> SymbolFactory<'b, C, P> {
       "/etc/nginx/snippets/acme-challenge.conf",
       format!(
         "location ^~ /.well-known/acme-challenge/ {{
-  alias {}/challenges/;
+  alias {}/;
   try_files $uri =404;
 }}",
         self.acme_factory.get_challenges_dir().to_str().unwrap()